Merge flipper.bredbandsbolaget.se:/home/marty/MySQL/mysql-5.0

into flipper.bredbandsbolaget.se:/home/marty/MySQL/mysql-5.1

BitKeeper/etc/logging_ok

@@ -140,6 +140,7 @@ magnus@msdesk.mysql.com
 magnus@neptunus.(none)
 magnus@shellback.(none)
 marko@hundin.mysql.fi
+marty@flipper.bredbandsbolaget.se
 marty@linux.site
 marty@shark.
 mats@mysql.com

mysql-test/README

@@ -2,8 +2,17 @@ This directory contains a test suite for mysql daemon. To run
 the currently existing test cases, simply execute ./mysql-test-run in
 this directory. It will fire up the newly built mysqld and test it.
 
-If you want to run the test with a running MySQL server use the --external
-option to mysql-test-run.
+If you want to run a test with a running MySQL server use the --extern
+option to mysql-test-run. Please note that in this mode the test suite
+expects user to specify test names to run. Otherwise it falls back to the
+normal "non-extern" behaviour. The reason is that some tests
+could not run with external server. Here is the sample command
+to test "alias" and "analyze" tests on external server:
+
+mysql-test-run --extern alias analyze
+
+To match your setup you might also need to provide --socket, --user and
+other relevant options.
 
 Note that you do not have to have to do make install, and you could
 actually have a co-existing MySQL installation - the tests will not

mysql-test/lib/mtr_cases.pl

@@ -154,6 +154,14 @@ sub collect_one_test_case($$$$$) {
     }
   }
 
+  if ( defined mtr_match_prefix($tname,"federated") )
+  {
+    $tinfo->{'slave_num'}= 1;           # Default, use one slave
+
+    # FIXME currently we always restart slaves
+    $tinfo->{'slave_restart'}= 1;
+  }
+
   # FIXME what about embedded_server + ndbcluster, skip ?!
 
   my $master_opt_file= "$testdir/$tname-master.opt";

mysql-test/r/insert_select.result

@@ -634,3 +634,18 @@ ff1	ff2
 1	2
 2	1
 drop table t1, t2;
+create table t1 (a int unique);
+create table t2 (a int, b int);
+insert into t1 values (1),(2);
+insert into t2 values (1,2);
+select * from t1;
+a
+1
+2
+insert into t1 select t2.a from t2 on duplicate key update a= a + t2.b;
+select * from t1;
+a
+2
+3
+drop table t1;
+drop table t2;

mysql-test/r/insert_update.result

-DROP TABLE IF EXISTS t1;
+DROP TABLE IF EXISTS t1, t2;
 CREATE TABLE t1 (a INT, b INT, c INT, UNIQUE (A), UNIQUE(B));
 INSERT t1 VALUES (1,2,10), (3,4,20);
 INSERT t1 VALUES (5,6,30) ON DUPLICATE KEY UPDATE c=c+100;

mysql-test/r/rpl_multi_update3.result

+stop slave;
+drop table if exists t1,t2,t3,t4,t5,t6,t7,t8,t9;
+reset master;
+reset slave;
+drop table if exists t1,t2,t3,t4,t5,t6,t7,t8,t9;
+start slave;
+CREATE TABLE t1 (
+a int unsigned not null auto_increment primary key,
+b int unsigned
+) ENGINE=MyISAM;
+CREATE TABLE t2 (
+a int unsigned not null auto_increment primary key,
+b int unsigned
+) ENGINE=MyISAM;
+INSERT INTO t1 VALUES (NULL, 0);
+INSERT INTO t1 SELECT NULL, 0 FROM t1;
+INSERT INTO t2 VALUES (NULL, 0), (NULL,1);
+SELECT * FROM t1 ORDER BY a;
+a	b
+1	0
+2	0
+SELECT * FROM t2 ORDER BY a;
+a	b
+1	0
+2	1
+UPDATE t2, (SELECT a FROM t1) AS t SET t2.b = t.a+5 ;
+SELECT * FROM t1 ORDER BY a;
+a	b
+1	0
+2	0
+SELECT * FROM t2 ORDER BY a;
+a	b
+1	6
+2	6
+SELECT * FROM t1 ORDER BY a;
+a	b
+1	0
+2	0
+SELECT * FROM t2 ORDER BY a;
+a	b
+1	6
+2	6
+drop table t1,t2;

mysql-test/t/insert_select.test

@@ -173,3 +173,17 @@ insert into t1 values (1),(1),(2);
 insert into t2(ff1) select f1 from t1 on duplicate key update ff2=ff2+1;
 select * from t2;
 drop table t1, t2;
+#
+# BUGS #9728 - 'Decreased functionality in "on duplicate key update"' 
+#      #8147 - 'a column proclaimed ambigous in INSERT ... SELECT .. ON
+#      DUPLICATE'
+#
+create table t1 (a int unique);
+create table t2 (a int, b int);
+insert into t1 values (1),(2);
+insert into t2 values (1,2);
+select * from t1;
+insert into t1 select t2.a from t2 on duplicate key update a= a + t2.b;
+select * from t1;
+drop table t1;
+drop table t2; 

mysql-test/t/insert_update.test

 --disable_warnings
-DROP TABLE IF EXISTS t1;
+DROP TABLE IF EXISTS t1, t2;
 --enable_warnings
 
 CREATE TABLE t1 (a INT, b INT, c INT, UNIQUE (A), UNIQUE(B));

mysql-test/t/rpl_multi_update3.test

+# Let's verify that multi-update with a subselect does not cause the slave to crash
+# (BUG#10442)
+
+source include/master-slave.inc;
+
+CREATE TABLE t1 (
+ a int unsigned not null auto_increment primary key,
+ b int unsigned
+) ENGINE=MyISAM;
+
+CREATE TABLE t2 (
+ a int unsigned not null auto_increment primary key,
+ b int unsigned
+) ENGINE=MyISAM;
+
+INSERT INTO t1 VALUES (NULL, 0);
+INSERT INTO t1 SELECT NULL, 0 FROM t1;
+
+INSERT INTO t2 VALUES (NULL, 0), (NULL,1);
+
+SELECT * FROM t1 ORDER BY a;
+SELECT * FROM t2 ORDER BY a;
+
+UPDATE t2, (SELECT a FROM t1) AS t SET t2.b = t.a+5 ;
+SELECT * FROM t1 ORDER BY a;
+SELECT * FROM t2 ORDER BY a;
+
+save_master_pos;
+connection slave;
+sync_with_master;
+SELECT * FROM t1 ORDER BY a;
+SELECT * FROM t2 ORDER BY a;
+
+drop table t1,t2;

mysys/my_access.c

@@ -93,18 +93,20 @@ int check_if_legal_filename(const char *path)
   path+= dirname_length(path);                  /* To start of filename */
   if (!(end= strchr(path, FN_EXTCHAR)))
     end= strend(path);
-  if (path == end || (uint) (path - end) > MAX_RESERVED_NAME_LENGTH)
+  if (path == end || (uint) (end - path) > MAX_RESERVED_NAME_LENGTH)
     DBUG_RETURN(0);                             /* Simplify inner loop */
 
   for (reserved_name= reserved_names; *reserved_name; reserved_name++)
   {
     const char *name= path;
-    while (name != end)
+    const char *current_reserved_name= *reserved_name;
+    
+    while (name != end && *current_reserved_name)
     {
-      if (my_toupper(&my_charset_latin1, *path) !=
-          my_toupper(&my_charset_latin1, *name))
+      if (*current_reserved_name != my_toupper(&my_charset_latin1, *name))
         break;
-      if (name++ == end)
+      current_reserved_name++;
+      if (++name == end)
         DBUG_RETURN(1);                         /* Found wrong path */
     }
   }

sql/ha_federated.cc

@@ -462,6 +462,12 @@ static int check_foreign_data_source(FEDERATED_SHARE *share)
   }
   else
   {
+    /*
+      Since we do not support transactions at this version, we can let the client
+      API silently reconnect. For future versions, we will need more logic to deal
+      with transactions
+    */
+    mysql->reconnect= 1;
     /* 
       Note: I am not using INORMATION_SCHEMA because this needs to work with < 5.0
       if we can connect, then make sure the table exists 
@@ -988,6 +994,12 @@ int ha_federated::open(const char *name, int mode, uint test_if_locked)
     my_error(ER_CONNECT_TO_MASTER, MYF(0), mysql_error(mysql));
     DBUG_RETURN(ER_CONNECT_TO_MASTER);
   }
+  /*
+    Since we do not support transactions at this version, we can let the client
+    API silently reconnect. For future versions, we will need more logic to deal
+    with transactions
+  */
+  mysql->reconnect= 1;
   DBUG_RETURN(0);
 }
 

sql/item.cc

@@ -338,6 +338,7 @@ Item::Item():
 	place == IN_HAVING)
       thd->lex->current_select->select_n_having_items++;
   }
+  item_flags= 0;
 }
 
 /*
@@ -358,7 +359,8 @@ Item::Item(THD *thd, Item *item):
   unsigned_flag(item->unsigned_flag),
   with_sum_func(item->with_sum_func),
   fixed(item->fixed),
-  collation(item->collation)
+  collation(item->collation),
+  item_flags(item->item_flags)
 {
   next= thd->free_list;				// Put in free list
   thd->free_list= this;

sql/item.h

@@ -225,6 +225,11 @@ typedef Item* (Item::*Item_transformer) (byte *arg);
 
 typedef void (*Cond_traverser) (const Item *item, void *arg);
 
+/*
+ See comments for sql_yacc.yy: insert_update_elem rule
+ */
+#define MY_ITEM_PREFER_1ST_TABLE 1
+
 class Item {
   Item(const Item &);			/* Prevent use of these */
   void operator=(Item &);
@@ -272,6 +277,7 @@ public:
   my_bool is_autogenerated_name;        /* indicate was name of this Item
                                            autogenerated or set by user */
   DTCollation collation;
+  uint8 item_flags;		/* Flags on how item should be processed */
 
   // alloc & destruct is done as start of select using sql_alloc
   Item();
@@ -584,6 +590,11 @@ public:
     cleanup();
     delete this;
   }
+  virtual bool set_flags_processor(byte *args)
+  {
+    this->item_flags|= *((uint8*)args);
+    return false;
+  }
 
   virtual bool is_splocal() { return 0; } /* Needed for error checking */
 };

sql/sql_base.cc

@@ -2628,7 +2628,6 @@ find_field_in_tables(THD *thd, Item_ident *item, TABLE_LIST *tables,
   uint length=(uint) strlen(name);
   char name_buff[NAME_LEN+1];
 
-
   if (item->cached_table)
   {
     /*
@@ -2695,10 +2694,13 @@ find_field_in_tables(THD *thd, Item_ident *item, TABLE_LIST *tables,
     db= name_buff;
   }
 
+  bool search_global= item->item_flags & MY_ITEM_PREFER_1ST_TABLE;
   if (table_name && table_name[0])
   {						/* Qualified field */
-    bool found_table=0;
-    for (; tables; tables= tables->next_local)
+    bool found_table=0;    
+    uint table_idx= 0;
+    for (; tables; tables= search_global?tables->next_global:tables->next_local,
+        table_idx++)
     {
       /* TODO; Ensure that db and tables->db always points to something ! */
       if (!my_strcasecmp(table_alias_charset, tables->alias, table_name) &&
@@ -2734,6 +2736,8 @@ find_field_in_tables(THD *thd, Item_ident *item, TABLE_LIST *tables,
 	    return (Field*) 0;
 	  }
 	  found=find;
+          if (table_idx == 0 && item->item_flags & MY_ITEM_PREFER_1ST_TABLE) 
+            break;
 	}
       }
     }
@@ -2758,9 +2762,10 @@ find_field_in_tables(THD *thd, Item_ident *item, TABLE_LIST *tables,
 	return (Field*) not_found_field;
     return (Field*) 0;
   }
-
   bool allow_rowid= tables && !tables->next_local;	// Only one table
-  for (; tables ; tables= tables->next_local)
+  uint table_idx= 0;
+  for (; tables ; tables= search_global?tables->next_global:tables->next_local, 
+      table_idx++)
   {
     if (!tables->table && !tables->ancestor)
     {
@@ -2795,7 +2800,9 @@ find_field_in_tables(THD *thd, Item_ident *item, TABLE_LIST *tables,
           my_error(ER_NON_UNIQ_ERROR, MYF(0), name, thd->where);
 	return (Field*) 0;
       }
-      found=field;
+      found= field;
+      if (table_idx == 0 && item->item_flags & MY_ITEM_PREFER_1ST_TABLE) 
+        break;
     }
   }
   if (found)

sql/sql_class.cc

@@ -156,9 +156,15 @@ bool foreign_key_prefix(Key *a, Key *b)
 /****************************************************************************
 ** Thread specific functions
 ****************************************************************************/
+/*
+  Pass nominal parameters to Statement constructor only to ensure that
+  the destructor works OK in case of error. The main_mem_root will be
+  re-initialized in init().
+*/
 
 THD::THD()
-  :user_time(0), global_read_lock(0), is_fatal_error(0),
+  :Statement(CONVENTIONAL_EXECUTION, 0, ALLOC_ROOT_MIN_BLOCK_SIZE, 0),
+   user_time(0), global_read_lock(0), is_fatal_error(0),
    rand_used(0), time_zone_used(0),
    last_insert_id_used(0), insert_id_used(0), clear_next_insert_id(0),
    in_lock_tables(0), bootstrap(0), derived_tables_processing(FALSE),
@@ -1483,9 +1489,10 @@ Query_arena::Type Query_arena::type() const
   Statement functions 
 */
 
-Statement::Statement(THD *thd)
-  :Query_arena(&main_mem_root, INITIALIZED),
-  id(++thd->statement_id_counter),
+Statement::Statement(enum enum_state state_arg, ulong id_arg,
+                     ulong alloc_block_size, ulong prealloc_size)
+  :Query_arena(&main_mem_root, state_arg),
+  id(id_arg),
   set_query_id(1),
   allow_sum_func(0),
   lex(&main_lex),
@@ -1494,33 +1501,7 @@ Statement::Statement(THD *thd)
   cursor(0)
 {
   name.str= NULL;
-  init_sql_alloc(&main_mem_root,
-                 thd->variables.query_alloc_block_size,
-                 thd->variables.query_prealloc_size);
-}
-
-/*
-  This constructor is called when Statement is a parent of THD and
-  for the backup statement. Some variables are initialized in
-  THD::init due to locking problems.
-*/
-
-Statement::Statement()
-  :Query_arena(&main_mem_root, CONVENTIONAL_EXECUTION),
-  id(0),
-  set_query_id(1),
-  allow_sum_func(0),                            /* initialized later */
-  lex(&main_lex),
-  query(0),                                     /* these two are set */ 
-  query_length(0),                              /* in alloc_query() */
-  cursor(0)
-{
-  /*
-    This is just to ensure that the destructor works correctly in
-    case of an error and the backup statement. The memory root will
-    be re-initialized in THD::init.
-  */
-  init_sql_alloc(&main_mem_root, ALLOC_ROOT_MIN_BLOCK_SIZE, 0);
+  init_sql_alloc(&main_mem_root, alloc_block_size, prealloc_size);
 }
 
 

sql/sql_class.h

@@ -817,13 +817,11 @@ public:
 
 public:
 
-  /*
-    This constructor is called when statement is a subobject of THD:
-    some variables are initialized in THD::init due to locking problems
-  */
-  Statement();
+  /* This constructor is called for backup statements */
+  Statement() { clear_alloc_root(&main_mem_root); }
 
-  Statement(THD *thd);
+  Statement(enum enum_state state_arg, ulong id_arg,
+            ulong alloc_block_size, ulong prealloc_size);
   virtual ~Statement();
 
   /* Assign execution context (note: not all members) of given stmt to self */
@@ -965,11 +963,6 @@ public:
   pthread_mutex_t LOCK_delete;		// Locked before thd is deleted
   /* all prepared statements and cursors of this connection */
   Statement_map stmt_map; 
-  /*
-    keeps THD state while it is used for active statement
-    Note: we perform special cleanup for it in THD destructor.
-  */
-  Statement stmt_backup;
   /*
     A pointer to the stack frame of handle_one_connection(),
     which is called first in the thread for handling a client

sql/sql_prepare.cc

@@ -1706,6 +1706,7 @@ bool mysql_stmt_prepare(THD *thd, char *packet, uint packet_length,
                         LEX_STRING *name)
 {
   LEX *lex;
+  Statement stmt_backup;
   Prepared_statement *stmt= new Prepared_statement(thd);
   bool error;
   DBUG_ENTER("mysql_stmt_prepare");
@@ -1739,13 +1740,13 @@ bool mysql_stmt_prepare(THD *thd, char *packet, uint packet_length,
     DBUG_RETURN(TRUE);
   }
 
-  thd->set_n_backup_statement(stmt, &thd->stmt_backup);
-  thd->set_n_backup_item_arena(stmt, &thd->stmt_backup);
+  thd->set_n_backup_statement(stmt, &stmt_backup);
+  thd->set_n_backup_item_arena(stmt, &stmt_backup);
 
   if (alloc_query(thd, packet, packet_length))
   {
-    thd->restore_backup_statement(stmt, &thd->stmt_backup);
-    thd->restore_backup_item_arena(stmt, &thd->stmt_backup);
+    thd->restore_backup_statement(stmt, &stmt_backup);
+    thd->restore_backup_item_arena(stmt, &stmt_backup);
     /* Statement map deletes statement on erase */
     thd->stmt_map.erase(stmt);
     DBUG_RETURN(TRUE);
@@ -1770,7 +1771,7 @@ bool mysql_stmt_prepare(THD *thd, char *packet, uint packet_length,
     transformation can be reused on execute, we set again thd->mem_root from
     stmt->mem_root (see setup_wild for one place where we do that).
   */
-  thd->restore_backup_item_arena(stmt, &thd->stmt_backup);
+  thd->restore_backup_item_arena(stmt, &stmt_backup);
 
   if (!error)
     error= check_prepared_statement(stmt, test(name));
@@ -1786,7 +1787,7 @@ bool mysql_stmt_prepare(THD *thd, char *packet, uint packet_length,
   lex_end(lex);
   close_thread_tables(thd);
   cleanup_stmt_and_thd_after_use(stmt, thd);
-  thd->restore_backup_statement(stmt, &thd->stmt_backup);
+  thd->restore_backup_statement(stmt, &stmt_backup);
   thd->current_arena= thd;
 
   if (error)
@@ -1949,6 +1950,7 @@ void mysql_stmt_execute(THD *thd, char *packet, uint packet_length)
 {
   ulong stmt_id= uint4korr(packet);
   ulong flags= (ulong) ((uchar) packet[4]);
+  Statement stmt_backup;
   Cursor *cursor;
   /*
     Query text for binary log, or empty string if the query is not put into
@@ -2026,8 +2028,7 @@ void mysql_stmt_execute(THD *thd, char *packet, uint packet_length)
   if (stmt->param_count && stmt->set_params_data(stmt, &expanded_query))
     goto set_params_data_err;
 #endif
-  thd->stmt_backup.set_statement(thd);
-  thd->set_statement(stmt);
+  thd->set_n_backup_statement(stmt, &stmt_backup);
   thd->current_arena= stmt;
   reinit_stmt_before_use(thd, stmt->lex);
   /* From now cursors assume that thd->mem_root is clean */
@@ -2064,7 +2065,7 @@ void mysql_stmt_execute(THD *thd, char *packet, uint packet_length)
     reset_stmt_params(stmt);
   }
 
-  thd->set_statement(&thd->stmt_backup);
+  thd->set_statement(&stmt_backup);
   thd->current_arena= thd;
   DBUG_VOID_RETURN;
 
@@ -2089,6 +2090,7 @@ void mysql_sql_stmt_execute(THD *thd, LEX_STRING *stmt_name)
     binary log.
   */
   String expanded_query;
+  Statement stmt_backup;
   DBUG_ENTER("mysql_sql_stmt_execute");
 
   DBUG_ASSERT(thd->free_list == NULL);
@@ -2110,16 +2112,16 @@ void mysql_sql_stmt_execute(THD *thd, LEX_STRING *stmt_name)
 
   /* Must go before setting variables, as it clears thd->user_var_events */
   mysql_reset_thd_for_next_command(thd);
-  thd->set_n_backup_statement(stmt, &thd->stmt_backup);
-  thd->set_statement(stmt);
+  thd->set_n_backup_statement(stmt, &stmt_backup);
   if (stmt->set_params_from_vars(stmt,
-                                 thd->stmt_backup.lex->prepared_stmt_params,
+                                 stmt_backup.lex->prepared_stmt_params,
                                  &expanded_query))
   {
     my_error(ER_WRONG_ARGUMENTS, MYF(0), "EXECUTE");
   }
   thd->command= COM_STMT_EXECUTE; /* For nice messages in general log */
   execute_stmt(thd, stmt, &expanded_query);
+  thd->set_statement(&stmt_backup);
   DBUG_VOID_RETURN;
 }
 
@@ -2176,7 +2178,6 @@ static void execute_stmt(THD *thd, Prepared_statement *stmt,
   close_thread_tables(thd);                    // to close derived tables
   cleanup_stmt_and_thd_after_use(stmt, thd);
   reset_stmt_params(stmt);
-  thd->set_statement(&thd->stmt_backup);
   thd->current_arena= thd;
 
   if (stmt->state == Query_arena::PREPARED)
@@ -2201,6 +2202,7 @@ void mysql_stmt_fetch(THD *thd, char *packet, uint packet_length)
   ulong stmt_id= uint4korr(packet);
   ulong num_rows= uint4korr(packet+4);
   Prepared_statement *stmt;
+  Statement stmt_backup;
   DBUG_ENTER("mysql_stmt_fetch");
 
   statistic_increment(thd->status_var.com_stmt_fetch, &LOCK_status);
@@ -2214,7 +2216,7 @@ void mysql_stmt_fetch(THD *thd, char *packet, uint packet_length)
   }
 
   thd->current_arena= stmt;
-  thd->set_n_backup_statement(stmt, &thd->stmt_backup);
+  thd->set_n_backup_statement(stmt, &stmt_backup);
 
   if (!(specialflag & SPECIAL_NO_PRIOR))
     my_pthread_setprio(pthread_self(), QUERY_PRIOR);
@@ -2226,7 +2228,7 @@ void mysql_stmt_fetch(THD *thd, char *packet, uint packet_length)
   if (!(specialflag & SPECIAL_NO_PRIOR))
     my_pthread_setprio(pthread_self(), WAIT_PRIOR);
 
-  thd->restore_backup_statement(stmt, &thd->stmt_backup);
+  thd->restore_backup_statement(stmt, &stmt_backup);
   thd->current_arena= thd;
 
   if (!stmt->cursor->is_open())
@@ -2386,7 +2388,9 @@ void mysql_stmt_get_longdata(THD *thd, char *packet, ulong packet_length)
 
 
 Prepared_statement::Prepared_statement(THD *thd_arg)
-  :Statement(thd_arg),
+  :Statement(INITIALIZED, ++thd_arg->statement_id_counter,
+             thd_arg->variables.query_alloc_block_size,
+             thd_arg->variables.query_prealloc_size),
   thd(thd_arg),
   param_array(0),
   param_count(0),

sql/sql_select.cc

@@ -1820,6 +1820,7 @@ Cursor::fetch(ulong num_rows)
   THD *thd= join->thd;
   JOIN_TAB *join_tab= join->join_tab + join->const_tables;
   enum_nested_loop_state error= NESTED_LOOP_OK;
+  Query_arena backup_arena;
   DBUG_ENTER("Cursor::fetch");
   DBUG_PRINT("enter",("rows: %lu", num_rows));
 
@@ -1831,7 +1832,7 @@ Cursor::fetch(ulong num_rows)
   thd->lock= lock;
   thd->query_id= query_id;
   /* save references to memory, allocated during fetch */
-  thd->set_n_backup_item_arena(this, &thd->stmt_backup);
+  thd->set_n_backup_item_arena(this, &backup_arena);
 
   join->fetch_limit+= num_rows;
 
@@ -1847,7 +1848,7 @@ Cursor::fetch(ulong num_rows)
     ha_release_temporary_latches(thd);
 #endif
 
-  thd->restore_backup_item_arena(this, &thd->stmt_backup);
+  thd->restore_backup_item_arena(this, &backup_arena);
   DBUG_ASSERT(thd->free_list == 0);
   reset_thd(thd);
 

sql/sql_yacc.yy

@@ -6120,9 +6120,24 @@ insert_update_elem:
 	simple_ident_nospvar equal expr_or_default
 	  {
 	  LEX *lex= Lex;
+          uint8 tmp= MY_ITEM_PREFER_1ST_TABLE;
 	  if (lex->update_list.push_back($1) || 
 	      lex->value_list.push_back($3))
 	      YYABORT;
+          /* 
+            INSERT INTO a1(a) SELECT b1.a FROM b1 ON DUPLICATE KEY 
+              UPDATE a= a + b1.b
+   
+            Set MY_ITEM_PREFER_1ST_TABLE flag to $1 and $3 items
+            to prevent find_field_in_tables() doing further item searching 
+            if it finds item occurence in first table in insert_table_list. 
+            This allows to avoid ambiguity in resolving 'a' field in 
+            example above.
+          */
+          $1->walk(&Item::set_flags_processor,
+                  (byte *) &tmp);
+          $3->walk(&Item::set_flags_processor,
+                  (byte *) &tmp);
 	  };
 
 opt_low_priority: